This invention relates to sealing glass compositions and, in particular, to such compositions for sealing alumina ceramic packages in which integrated circuits or other solid state devices are encapsulated.
As a known sealing glass composition for sealing alumina ceramic packages, there has been used one which comprises a devitrifying solder glass and zircon (zirconium silicate, ZrSiO.sub.4). Since the sealing glass of this type requires a long sealing time and high sealing temperature, it is uneconomical with respect to heat energy. Furthermore, it has been recently discovered that .alpha.-ray radiated from radioactive impurities included in the zircon causes soft errors of the integrated circuit.
Another known type of sealing glass composition comprises vitreous solder glass and .beta.-eucryptite or lead titanate. The sealing glass of this type is more desirable because it requires shorter sealing time and lower sealing temperature. But the glass composition including .beta.-eucryptite is poor in acid resistance, and tends to degrade in electric resistance during long exposure to an environment of a high temperature and a high humidity. The glass composition including lead titanate has high dielectric constant and, therefore, cannot be used for high frequency applications.